JPS62127779A - Toner concentration detecting device - Google Patents

Abstract

PURPOSE:To always obtain the output signal of the constant level by amplifying the output of a concentration sensor to detect the concentration of a toner image with plural amplifier circuits in which the amplifying degree is set respectively in accordance with the sensitivity of the concentration sensor to the color of respective developers. CONSTITUTION:The detecting signal outputted from a concentration sensor 26 through amplifier circuits 27-30 [(red), (yellow), green, and (blue) in order] and an amplifier circuit selecting means 34 provided by the number only in accordance with the number of the color of the developer used to a control part 31. In the control part 31, it is discriminated whether or not the concentration of the toner image based on the detecting signal is the reference value, when it is discriminated that the concentration of the toner image is the reference value or below, a toner supplying command signal is outputted to a developing part 15, the rate of the toner in the developer is increased and the control is executed so as to make thicker the concentration of the toner image. Thus, the output of the concentration sensor is amplifier in accordance with the sensitivity to respective colors, and when the concentration of the toner image is the reference value, the output signal of the constant level can always be obtained.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus configured to convert an electrostatic latent image formed on a photoreceptor into a toner image using a plurality of color developers. This invention relates to an improvement of a toner concentration detection device.

(Prior art) Conventionally, an image is created by converting an electrostatic latent image on a photoreceptor (electrostatic image carrier) into a toner image, detecting its density, and adjusting toner supply δ based on the detected value. For example, Japanese Patent Laid-Open No. 56-12
No. 8977). Further, in an image forming apparatus configured to perform so-called multiple printing using developers of multiple colors, the sensitivity of a density sensor made of a photosensor changes depending on the color of the developer used. For this reason, density sensors are provided in a number corresponding to the number of developer colors, and the sensor output is always at a constant level when the density of the toner image of each color is at the reference value. Efforts are being made to accurately detect and properly control the concentration. This configuration has the problem that manufacturing costs are high because a plurality of sensors are required, and a large space is required to install the plurality of sensors, resulting in an increase in the size of the device.

(Object of the Invention) The present invention has been made in order to solve the above-mentioned problems, and by making it possible to appropriately detect the density of each color toner image with a single m degree sensor, it is possible to solve the problems described above. The present invention provides a toner concentration detection device that can be downsized.

(Structure of the Invention) The present invention is a toner quality detection device in an image forming apparatus configured to convert an electrostatic latent image formed on a photoreceptor into a toner image using a plurality of color developers, comprising: It is equipped with a density sensor that detects the density of a toner image and an amplifier circuit that amplifies the output of this density sensor. These settings are made according to the sensitivity of the density sensor to color.

With this configuration, aI! The output of the t-sensor is amplified according to the sensitivity to each color, and when the density of the toner image is at the reference value, an output signal at the set level can always be obtained.

(Embodiment) FIG. 1 schematically shows the internal structure of an electrostatic copying machine, in which 1 is a contact glass, 2 is an optical system section, and 3 is a photosensitive drum. The optical system section 2 includes an original black lamp 4, a reflection plate 5, first to third mirrors 6 to 8, and a condensing lens 9.
and a fourth mirror 10, the document irradiation lamp 4 and the like move back and forth along the lower surface of the contact glass 1, and are configured to expose the document 11 on the contact glass 1 during the reciprocation.

The photosensitive drum 3 is moved by an arrow X by a drive mechanism (not shown).
rotationally driven in the direction. A main charging section 13 having a charge wire R12, a developing section 15 having a developing roller 14, a transfer charging section 16, a separation charging Fi 517, and a cleaning section 18 are arranged around the photosensitive drum 3. . As the photoreceptor drum 630 rotates, the surface of the photoreceptor drum 3 is charged by the charge wire 12 to which a high voltage is applied in the main charging section 13, and the document is transferred from the optical system section 2 onto the photoreceptor drum 3. The image is illuminated to form an electrostatic latent image.

After this electrostatic latent image is converted into a toner image by the developing section 15, it is fed out from the paper feed cassette 19 and placed on the registration rollers 2.
0 and the transfer paper fed through the pre-transfer roller 21,
The image is transferred by the transfer charging section 16 . This transfer paper is separated from the photoreceptor drum 3 by the separating and charging section 17, and then sent to the fixing section 23 by the ejection belt 22, and then transferred to the paper ejection tray 2.
4. A limit switch 25 is provided between the registration roller 20 and the pre-transfer roller 21 to detect when the recording paper fed out from the paper feed cassette 19 reaches -521 copies of the day before transfer.

The developing section 15 is removably attached to the body of the electrostatic copying machine, and can be replaced with a developing section containing a different color developer as needed to form a toner image of a different color. It has become.

Further, a concentration sensor 26 consisting of a photosensor is disposed between the separation charging section 17 and the cleaning section 18,
This density sensor 26 detects the density of the toner image corresponding to the simulated original mA provided on the lower surface of the contact glass 1. That is, by irradiating light from the light emitting section of the density sensor 26 onto the toner image of the simulated original A formed on the photoreceptor drum 3t, and detecting the amount of reflected light at the light receiving section, the density of the toner image is determined as the standard. It is designed to detect whether the value is within the appropriate value (appropriate value).

As shown in FIG. 2, the detection signal output from the density sensor 26 is transmitted to the amplifier circuits 27, 28, 29, 30 and the amplifier circuit selection means 34, which are provided in a number corresponding to the number of colors of the developer used. The data is input to the aIIjt11 section 31 through the. Then, in this control section 31, it is determined whether the density of the toner image is at the base Fp value based on the above-mentioned detection signal, and if it is determined that the density of the toner image is below the reference value, the developing section 15 A toner replenishment command signal is output, and control is performed to increase the ratio of toner in the developer to increase the density of the toner image. Note that, instead of the toner replenishment command signal, a control signal for adjusting the light a of the document irradiation lamp 4 or the bias voltage of the developing roller 14 may be outputted from the control section 31.

As shown in FIG. 3, the sensitivity of the density sensor 26 changes depending on the color of the developer used, and is designed to have the best sensitivity for red (wavelength around 600) images from 1 to 2. When set to
Sensitivity gradually decreases for toner images of around 50 people. Therefore, by setting the amplification degree of each of the amplification circuits 27 to 30 according to the sensitivity of the corresponding developer color, the ability of the density sensor 26 can be utilized to the maximum, and the density of the toner image of each color can be maximized. When is at the reference value, a detection signal of a constant level is always input to the control section 31.

That is, the amplifier circuits 28 to 30 corresponding to colors other than red
By setting the amplification degree of the amplification circuit 27 larger than the amplification degree of the amplification circuit 27 corresponding to red color according to the rate of decrease in sensitivity, the level of the detection signal output when the l-ner image is at the reference density can be increased. It is configured to be constant for all colors.

Therefore, there is no need to provide multiple density sensors depending on the number of colors of the developer used, and there is no need for problems such as uncertain control depending on low-level output signals. Appropriate control can be performed with a simple configuration.

Further, as shown in FIG. 4, a developer color display mark 32 is formed on the outer surface of the side wall of the developing section 15, and this is detected by a developing section detecting means 33 consisting of a photosensor or lead switch, and the detection signal is If configured so that the color of the developer to be used is input to the amplifier circuit selection means 34, the colors of the developer to be used are sequentially displayed, and accordingly, the one among the amplifier circuits 27 to 30 that should be outputted as a signal to the control section 31 is automatically selected. can do.

FIG. 5 shows an embodiment in which the density sensor 26 has the function of detecting the winding of the transfer paper around the photosensitive drum 3. That is, based on the signal output from the clock timer 35, the density sensor 2
6 to the circumferential surface of the photoreceptor drum 3, and the controller 31 determines the presence or absence of the transfer paper based on the reflected light R, whereby the transfer paper is separated via the separation charging unit 17. Detect whether it is done well. If a separation failure occurs and the transfer paper wraps around the photoreceptor drum 3, it is configured to output an output signal to the drive section 36 to stop the copying operation.

If the sensitivity of the density sensor 26 is set to be the best for red toner images as in the above embodiment, the sensitivity of the sensor 26 will also decrease once for light reflected from the transfer paper. Therefore, by providing an amplification circuit 37 having an amplification degree corresponding to the rate of decrease in sensitivity, the output level of the concentration sensor 26 output when detecting winding can be kept at an appropriate value. It is desirable to set this.

Note that the amount of the reflected light differs depending on whether plain paper is used as the transfer paper or special paper such as tracing vapor or transparent film is used, and the sensitivity of the density sensor 26 also changes depending on the paper quality. Therefore, by providing and selectively using amplifier circuits each having an amplification degree corresponding to each paper quality, more accurate detection of transfer paper wrapping becomes possible.

(Effects of the Invention) As explained above, the present invention allows the output of a density sensor that detects the density of a toner image to be sent to a plurality of sensors each having an amplification degree set according to the sensitivity of the density sensor to each developer color. Since the amplification circuit is used for amplification, it is possible to always obtain an output signal at a constant level when the toner image is at the level of 1. Therefore, there is no need to provide multiple density sensors depending on the number of colors of the developer used.
The density sensor of A-1 can accurately detect and control whether the density of each color toner image is within the standard value, and by minimizing the number of density sensors and their installation space, %j Fj ] This has the effect of reducing costs and downsizing the device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an electrostatic copying machine equipped with a toner concentration detection device according to the present invention, FIG. 2 is a block diagram showing the configuration of the toner concentration detection device, and FIG. FIG. 4 is a graph showing the relationship between the sensitivity of the sensor and the color of the toner image, FIG. 4 is a perspective view showing the developing section detection means, and FIG. 5 is a block diagram of another embodiment of the toner concentration detection device. 3... Photosensitive drum, 26... Density sensor, 27.
28.29.30...it'l#A circuit. Patent applicant Agent: Sanda Kogyo Co., Ltd.
Patent Attorney Etsushi Kotani Patent Attorney Long 1) Front Patent Attorney Ino Itaya Figure 4

Claims (1)

[Claims] 1. A toner density detection device for an image forming apparatus configured to convert an electrostatic latent image formed on a photoreceptor into a toner image using a plurality of color developers, the device detecting the density of the toner image. It is equipped with a sensor and an amplifier circuit that amplifies the output of the density sensor, and the amplification degree of the plurality of amplifier circuits provided according to the number of developer colors used is adjusted according to the sensitivity of the density sensor to each developer color. A toner concentration detection device characterized in that each of the toner density detection devices is set as follows.